Seed Biopriming With Trichoderma Strains Isolated From Tree Bark Improves Plant Growth, Antioxidative Defense System in Rice and Enhance Straw Degradation Capacity

Abstract

This study is a unique report of the utilization of <i>Trichoderma</i> strains collected from even tree barks for rice plant growth, its health management, and paddy straw degradation. Seven different spp. of <i>Trichoderma</i> were characterized according to morphological and molecular tools. Two of the isolated strains, namely <i>Trichoderma hebeiensis</i> and <i>Trichoderma erinaceum</i>, outperformed the other strains. Both of the strains controlled four important rice pathogens, i.e., <i>Rhizoctonia solani</i> (100%), <i>Sclerotium oryzae</i> (84.17%), <i>Sclerotium rolfsii</i> (66.67%), and <i>Sclerotium delphinii</i> (76.25%). Seed bio-priming with respective <i>Trichoderma</i> strains reduced the mean germination time, enhanced the seedling vigor and total chlorophyll content which could be related to the higher yield observed in two rice varieties; Annapurna and Satabdi. All the seven strains accelerated the decomposition of rice straw by producing higher straw degrading enzymes like total cellulase (0.97-2.59 IU/mL), endoglucanase (0.53-0.75 IU/mL), xylanase (145.35-201.35 nkat/mL), and laccase (2.48-12.60 IU/mL). They also produced higher quantities of indole acetic acid (19.19-46.28 μg/mL), soluble phosphate (297.49-435.42 μg/mL), and prussic acid (0.01-0.37 μg/mL) which are responsible for plant growth promotion and the inhibition of rice pathogen populations. Higher expression of defense enzymes like catalase (≥250% both in shoot and root), peroxidase (≥150% in root and ≥100% in shoot), superoxide dismutase (≥ 150% in root and ≥100% in shoot), polyphenol oxidase (≥160% in shoot and ≥120% in shoot), and total phenolics (≥200% in root and ≥250% in shoot) as compared to the control indicates stress tolerance ability to rice crop. The expression of the aforementioned enzymes were confirmed by the expression of corresponding defense genes like PAL (>3-fold), DEFENSIN (>1-fold), POX (>1.5-fold), LOX (>1-fold), and PR-3 (>2-fold) as compared to the non-treated control plants. This investigation demonstrates that <i>Trichoderma</i> strains obtained from tree bark could be considered to be utilized for the sustainable health management of rice crop.